我的应用程序在应用程序退出时崩溃。 除了如果歌曲正在播放，而你退出，它永远不会崩溃。 但是如果歌曲没有播放/播放，而我退出了应用程序，它就会退出并崩溃。 我在ondestroy函数中杀死了你的任务activity。 请帮帮我。

这是TIP1活动，Java

public class Tip1Activity extends AppCompatActivity {
    private ArrayList<Music> arrayList;
    private CustomMusicAdapter adapter;
    private RecyclerView recyclerView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tip1);



        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        recyclerView =  findViewById(R.id.recyclerViewList);

        arrayList = new ArrayList<>();
        arrayList.add(new Music("001 Veni, veni, Emmanuel", "SONGS OF WORSHIP", R.raw.veni_emmanuel));
        arrayList.add(new Music("002 O come. O come Emmanuel", "SONGS OF WORSHIP", R.raw.o_come_emmanuel));
        arrayList.add(new Music("003 Savior of the nations, come", "SONGS OF WORSHIP", R.raw.savior_of_nations));
        arrayList.add(new Music("004 On Jordan's bank the Baptist's cry", "SONGS OF WORSHIP", R.raw.on_jordans_bank));
        arrayList.add(new Music("005 Lo, he comes", "SONGS OF WORSHIP", R.raw.lo_he_comes));
        arrayList.add(new Music("006 O Word that goest forth on high", "SONGS OF WORSHIP", R.raw.o_word_that_goes_forth));
        arrayList.add(new Music("007 Wake, awake", "SONGS OF WORSHIP", R.raw.wake_awake));
        arrayList.add(new Music("008 Rorate caeli", "SONGS OF WORSHIP", R.raw.rorate_caeli));
        arrayList.add(new Music("009 Conditor alme siderum", "SONGS OF WORSHIP", R.raw.conditor_alme_siderum));
        arrayList.add(new Music("010 Creator of the stars of night", "SONGS OF WORSHIP", R.raw.creator_of_the_stars));



        adapter = new CustomMusicAdapter(this, R.layout.custom_music_row, arrayList);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setHasFixedSize(false);

    }



    public void onDestroy() {
        super.onDestroy();
        if( adapter !=null ){
            adapter.release();
        }
    }

    @Override
    public void onBackPressed() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Do you want to close App?")
                .setCancelable(false)
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        Tip1Activity.this.finish();
                    }
                })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });
        AlertDialog alert = builder.create();
        alert.show();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);

        MenuItem menuItem = menu.findItem(R.id.search_view);

        SearchView searchView = (SearchView) menuItem.getActionView();

        searchView.setMaxWidth(Integer.MAX_VALUE);

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {

                adapter.getFilter().filter(newText);
                return true;
            }
        });



        return  true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){

            case R.id.item1:
                Toast.makeText(this, "Settings Selected", Toast.LENGTH_SHORT).show();
                startActivity(new Intent(this, Main2Activity.class));
                return true;

            //DO YOUR FUNCTIONALITY HERE




            default:
                return super.onOptionsItemSelected(item);
        }

    }
}

customMusicAdapter.java

public class CustomMusicAdapter extends RecyclerView.Adapter<MyViewHolder> implements Filterable {

    private Context context;
    private int layout;
    private ArrayList<Music> myArraylist;
    private ArrayList<Music> getUserModelListFiltered;
    private static MediaPlayer mediaPlayer;
    private boolean flag=true;


    public CustomMusicAdapter(Context context, int custom_music_row, ArrayList<Music> myArraylist) {
        this.context = context;
        this.layout = layout;
        this.getUserModelListFiltered = myArraylist;
        this.myArraylist = myArraylist;

    }

    public void release(){
        mediaPlayer.stop();
        mediaPlayer.release();
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        final View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.custom_music_row, parent, false);
        return new MyViewHolder(itemView);
    }



    @SuppressLint("RecyclerView")
    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
        holder.setIsRecyclable(false);

        final Music music = myArraylist.get(position);
        holder.mTitle.setText(music.getName());
        holder.mDes.setText(music.getSinger());

        //Play Music Setup
        holder.mImageaplay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if (flag){
                    mediaPlayer=MediaPlayer.create(context,music.getSong());
                    flag=false;
                }
                if (mediaPlayer.isPlaying()){
                    mediaPlayer.pause();
                    mediaPlayer.start();
                    holder.mImageaplay.setImageResource(R.drawable.ic_play);
                }else {
                    mediaPlayer.start();
                    holder. mImageaplay.setImageResource(R.drawable.ic_pause);
                }
                mediaPlayer.start();

            }
        });

        // stop player
        holder.mImageStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (!flag){
                    mediaPlayer.stop();
                    mediaPlayer.release();
                    flag=true;
                }
                holder.mImageaplay.setImageResource(R.drawable.ic_play);
            }
        });

    }

    @Override
    public int getItemCount() {
        return myArraylist.size();
    }

    @Override
    public Filter getFilter() {

        Filter filter = new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence charSequence) {
                FilterResults filterResults = new FilterResults();
                if (charSequence == null | charSequence.length() == 0){
                    filterResults.count = getUserModelListFiltered.size();
                    filterResults.values = getUserModelListFiltered;
                }else {
                    String searchChr = charSequence.toString().toLowerCase();
                    List<Music> resultData = new ArrayList<>();
                    for (Music music: getUserModelListFiltered){
                        if (music.getName().toLowerCase().contains(searchChr)){
                            resultData.add(music);
                        }
                    }
                    filterResults.count = resultData.size();
                    filterResults.values = resultData;
                }
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence charSequence, FilterResults filterResults) {

                myArraylist = (ArrayList<Music>) filterResults.values;
                notifyDataSetChanged();

            }
        };
        return filter;
    }

    public class ViewHolder {
        TextView textView_SongName, textView_artist;
        ImageView imageView_play, imageView_stop;
        private View convertview;
        LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);

        public ViewHolder() {
            convertview = layoutInflater.inflate(layout, null);
            textView_SongName = convertview.findViewById(R.id.textName);
            textView_artist = convertview.findViewById(R.id.txtSinger);
            imageView_play = convertview.findViewById(R.id.ivPlay);
            imageView_stop = convertview.findViewById(R.id.ivStop);

        }
    }
}

这是LogaCat

2020-06-24 12:44:35.598 27137-27137/com.josephgritchen.songsofworship E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.josephgritchen.songsofworship, PID: 27137
    java.lang.RuntimeException: Unable to destroy activity {com.josephgritchen.songsofworship/com.josephgritchen.songsofworship.Tip1Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
        at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4425)
        at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:4443)
        at android.app.ActivityThread.-wrap5(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1684)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6549)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
        at com.josephgritchen.songsofworship.CustomMusicAdapter.release(CustomMusicAdapter.java:38)
        at com.josephgritchen.songsofworship.Tip1Activity.onDestroy(Tip1Activity.java:67)
        at android.app.Activity.performDestroy(Activity.java:7239)
        at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1249)
        at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4412)
        at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:4443) 
        at android.app.ActivityThread.-wrap5(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1684) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6549) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888) 

这就是我所做的仍然给我带来错误的事

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// stop player
        holder.mImageStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mediaPlayer!=null)
                {
                    if(mediaPlayer.isPlaying())
                    {
                        mediaPlayer.stop();
                        mediaPlayer.release();
                    }
                holder.mImageaplay.setImageResource(R.drawable.ic_play);
            }}

        });

    }

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